http://www.post-gazette.com/pg/11263/1176161-100.stm
PedOncoDoc
09-20-2011, 11:40
The illness, caused by the bacterium Salmonella Typhi, can be contracted when a person ingests water contaminated by sewage or food that's been handled by someone shedding the bacteria.
Not surprising this came from a recently-arrived foreign student. This illness typically is shed in feces and can pollute water sources in undeveloped living areas. As the article mentions, you don't catch it by not sharing food/drink, routine hand washing and drinking properly handled water.
Basically, you get it from eating shit, intentionally or otherwise.